(1) Field of the Invention
The present invention relates to a printer ribbon and a film used for the preparation thereof. More particularly, it relates to a film used for the preparation of a printer ribbon, the demand for which is increasing with the recent development of typewriters, word processors and the like, and which film is prepared by the T-die-chill roll method.
(2) Description of the Related Art
As the substrate of a printer ribbon, there have been heretofore used fabrics of silk, cotton and nylon. These substrates have problems in that the printing characteristics are poor, the printing speed is low, the thickness is large, and the printing precision is low.
As the consumption of printer ribbons increases with the development of typewriters, word processors and the like, there is a strong demand for a reduction of the printing cost per word. Under these circumstances, use of a polyolefin film, for example, a high-density polyethylene film as the substrate of a printer ribbon has been recently attempted.
As a means for preparing these polyolefin films, there is known, for example, the T-die-chill roll method. The T-die-chill roll method is a film-preparing method in which a thermoplastic synthetic resin film extruded from a T-die is cooled by contact with a rotary chill roll, through the interior of which is ordinarily passed circulated cooling water.
According to this T-die-chill roll method, air is readily engulfed between the chill roll and the molten resin film, and because of an insufficient contact between the roll and the molten resin film, the film thickness is often uneven and wrinkles are readily formed on the film surface. Furthermore, since cooling is insufficient, the transparency or surface gloss is degraded. This tendency is conspicuous in the high-speed forming operation or the thin film-forming step, and if this film is used for a printer ribbon, problems such as a reduction of the printing characteristics, insufficient coating with an ink, and insufficient slitting arise.